Testing of communication lines, such as telephone lines and network cables is a vital function for operation of communication systems. Typically. testing involves determining the operational status of a communication line. For instance, for a twisted pair telephone line, operational status would include the length of the twisted pair line, the number and location of any taps or splices on the line, and the level of attenuation that the line imposes upon a communication signal traveling across the line.
To determine operational status of a communication line, test equipment is typically placed on both ends of the line. In the case of a twisted pair telephone line, one end is generally located at a central office site, and the other end is usually located either at a residential or commercial establishment. Prior art dual-ended testing systems and methods that use testing equipment on both ends of a communication line are inherently more costly and logistically complex to implement than a single-ended testing system that requires testing equipment on only one end of a communication line. However, prior art systems have focused on dual-ended testing rather than single-ended testing because of difficulties imposed by single-ended testing.
Both dual and single-ended testing share some similar problems related to testing. Some testing problems are caused by anomalous signals being introduced by the test equipment itself on to the communication line being tested. Other measurement problems are caused by signal noise. These and other conditions adversely affect accuracy of measurements. Other related difficulties that users of the test equipment face involve poor presentation by test equipment of the test results. The poor presentation of test data is in part caused by factors that corrupt the test measurements that produced the test data. As a result, users are forced to waste time manipulating controls to obtain meaningful pictures of the test results. Often after much adjustment of controls the users have to settle for less than desirable views of somewhat suspect test data.
These problems have been obstacles to adoption of single-ended testing as a general test method for more than time domain reflectometry. Even time domain reflectometry still suffers from presentation problems. Other test measurements, such as those involving signal power measurements including signal attenuation or signal-to-noise ratios, have not found favor with single-ended testing because the problems caused by such things as anomalous signals or noise are potentially compounded for single-ended testing given the doubling of travel of a test signal compared to dual-ended testing. Test signals are harder to recover by the further attenuation involved, and anomalous signals and noise can have even greater corrupting influence on measurements.